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EducationWhat Is Peptide Therapy?
A research-based overview of what peptides are, how they work biologically, what the evidence currently supports, and what to expect if you're exploring treatment.
PSI is an independent research platform. This page is educational and does not constitute medical advice. Consult a licensed physician before beginning any peptide therapy protocol.
The basics
Peptides are short chains of amino acids, the same building blocks that make up proteins. Your body produces thousands of peptides naturally. They act as biological messengers, telling cells to repair tissue, regulate hormones, modulate immune responses, and carry out hundreds of other functions.
Peptide therapy uses synthetically produced versions of these compounds (administered by injection, nasal spray, or topically) to influence specific biological pathways. The goal is to support or restore signaling that may be diminished due to age, injury, or disease.
How peptides differ from hormones and steroids
Peptides are not hormones, though some influence hormone production. They are not anabolic steroids, which directly replace or amplify hormones artificially. Peptides work upstream, signaling the body to regulate its own processes. This distinction matters for both mechanism and risk profile.
What the research currently supports
Evidence quality varies significantly by compound. A small number of peptides have robust clinical trial data and FDA approval. Most have preliminary or moderate evidence from animal studies and small human trials. PSI categorizes every compound by evidence level, from Preclinical (theoretical) to FDA Approved (FDA approved with large-scale trials).
The most evidence-backed peptides in clinical use include semaglutide and tirzepatide (metabolic health), sermorelin (growth hormone deficiency), and BPC-157 (tissue repair, early human data).
Who uses peptide therapy
Three broad groups: people managing specific medical conditions (GH deficiency, obesity, metabolic disease), athletes and longevity-focused individuals exploring performance and recovery optimization, and researchers and clinicians studying peptide mechanisms. PSI serves all three without commercial bias.
What to expect from treatment
Peptide therapy requires a physician's prescription in the United States. A qualified physician will evaluate your labs, health history, and goals before recommending a protocol. Most injectable peptides are self-administered subcutaneously. Effects are typically gradual, most protocols run 3-6 months before meaningful assessment.